Cron is used to execute scheduled commands. It acts as a task scheduler on Linux and UNIX systems which will execute commands at specified times set by the user. Cron has a great deal of customization and is often used on server environments where common tasks are run on a regular basis.

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How do I set up a Cron job?

I want to schedule a task to run on a regular basis and have heard that Cron is the way to do this. How do I add Cron jobs in Ubuntu?
278
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40answers
448k views

Reasons why crontab does not work

Often, crontab scripts are not executed on schedule or as expected. There are numerous reasons for that: wrong crontab notation permissions problem environment variables This community wiki aims ...
8
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2answers
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How to start a GUI application from cron?

I need to run a Java applet from a Firefox. The problem is, I need to run this Firefox from a cron. If I run from the command line and its work fine, but when put the command in the cron it failed: */...
355
votes
5answers
692k views

Where is the cron / crontab log?

I want to verify if my cron job is executing and what time. I believe there is a log for my sudo crontab -e jobs, but where? I searched google and it I found references to look in /var/log (...
50
votes
5answers
55k views

How are administrators supposed to read root's mail?

What is the Ubuntu way for system administrators to receive system notifications, which typically take the form of e-mail sent to the root account? Examples of such notifications are the output of ...
53
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3answers
96k views

How to run a cron job using the sudo command

Is it possible to run a cron job which needs the sudo command? Like: sudo rm somefile
8
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5answers
19k views

cron.daily jobs not running

I created 3 daily cron jobs to run. Below are the three that are placed in etc/cron.daily rkhunter.sh #!/bin/sh ( rkhunter --versioncheck rkhunter --update rkhunter --cronjob --report-warnings-only ...
71
votes
6answers
121k views

“(CRON) info (No MTA installed, discarding output)” error in the syslog

I have a fresh install of Ubuntu 12.04.1 LTS an a number of servers. I have not added any cron jobs or edited my crontab on those servers, however, at around the same time for each machine, I get a ...
114
votes
4answers
176k views

Where is the user crontab stored?

Since upgrading my user's crontab has been wiped out. This is not the first time this has happened this year and it's a pain restoring it each time. I'd like to be able to back up the crontab for my ...
18
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3answers
55k views

How to execute command every 10 seconds (without cron)?

When I execute cron I get this fault cron: can't open or create /var/run/crond.pid: Permission denied So, how to do it without cron? P.S. I want to check if file in svn has changed and I have a ...
6
votes
3answers
3k views

Programmatically sync dropbox without daemon running

I would like to 'manually' force dropbox to sync at certain times (eg at regular, daily intervals using cron, as part of a larger backup script). My goal is to substitute the dropbox daemon with ...
3
votes
1answer
9k views

Stop cron from mailing the user

I am facing an issue with Ubuntu server. I am running a PHP script using a cron job which executes every 5 minutes. This folder spool/mqueue is showing 112GB space. The scripts job is to fetch data ...
4
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3answers
18k views

Getting output from a cron job on the terminal

I have a program that prints some output that I would like to pop up on my terminal once every hour during the workday. $ crontab -l 0 07-17 * * * /home/dat/scripts/cron.out syslog reports the ...
10
votes
1answer
8k views

Does ubuntu support “@reboot” in crontab

Does ubuntu support "@reboot" in crontab ? I find documentation suggesting it is supported, but web chatter asserts it is not. I cannot make the @reboot section work. The "after midnight" section ...
9
votes
2answers
385 views

Make a new archive once per minute using “crontab”

I am trying to make a crontab that makes a new .tar file each minute every business day by using the following code: */1 * * * 1,2,3,4,5 tar -cf /home/user/Archiv/$(date +"%Y%m%d%H%M").tar /home/user/...
23
votes
2answers
128k views

Script doesn't run via crontab but works fine standalone

I have a script that reminds me to restart my computer if uptime is more than, say 3 days (although its set to 0 days now just to check if the script is running as my computer has been up only over a ...
33
votes
5answers
27k views

Cron.hourly won't run

Ok, So I've made my script, I dropped it in /etc/cron.hourly then I chmod 777 the file but it won't run (automatically). If I manually run it, it works fine. Do I need to do anything else?
20
votes
1answer
23k views

Add lines to cron from script

Is there a way to add lines to a user's cron via script? I usually do it using crontab -e, but I would like to automate this task with a shell script.
12
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3answers
20k views

How can I setup a Mail Transfer Agent?

I intend to use mutt to send automated emails via cron or at with attachments to my gmail address when particular events happen on my Ubuntu server. Currently, mutt cannot send email to external ...
11
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2answers
60k views

How can I see/stop current running crontab tasks?

How can I see crontab tasks which are in progress? How can I stop crontab tasks which are in progress, manually? Is [this] question about see the current running cron processes? Yes To kill ...
6
votes
5answers
85k views

How to Setup a root cron Job Properly

I tried to setup a root cron job to run a Bash script as root, to run at minute 7,37, every hour, every day of month, every month. This script is located in /usr/bin and named tunlrupdate.sh is used ...
10
votes
3answers
13k views

Why is this rsync + ssh cron job giving me 'Permission denied (publickey)' errors?

I make frequent backups to a local drive which I want to sync daily to a remote server. The target server is configured for SSH key (no password) access only. Since my primary SSH key for that server ...
6
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2answers
4k views

Automating duplicity backups using cron

How do I automate duplicity backups using cron using gpg encryption and the ssh backend?
16
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3answers
11k views

Can symlinks be used in /etc/cron.d/?

I'm trying to implement a configuration mechanism that allows in a certain project to deploy through svn a cron configuration. I immediately thougt that what I should do is cerate symlinks from /etc/...
14
votes
1answer
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What is the story behind the default times set in /etc/crontab?

To my understanding, this is the default configuration of /etc/crontab: # m h dom mon dow user command 17 * * * * root cd / && run-parts --report /etc/cron.hourly 25 6 * * * ...
4
votes
1answer
4k views

shut down linux server and turn on automatically at specific time

I'm having an assignment where the lecturer is asking me to create a bash script to shut down a server at 11pm and turn it on at 6am. I'm able to do it by using sudo shutdown -h 23:00 and it works. ...
2
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1answer
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Schedule to turn off monitor via crontab?

I want to turn off monitor on a specific period of time automatically (for example between 07:00 and 11:00). Is there any command to be set in crontab file? Is there any better way? In summary: ...
1
vote
1answer
212 views

Cron fails at night

I have set up a cron job, but for some reason it fails to run during the night. The same job runs fine when i'm running it during the day (i.e. setting up the same job to run in a few minutes and ...
0
votes
1answer
161 views

How to tell cron to find paths to tools?

Is there a way to indicate to cron how/where to find (paths to) tools such as python, nmap, php and so on? I ask this because when I schedule a job using crontab -e, I always need to specify the ...
42
votes
7answers
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Changing default crontab editor

I am trying to change the default editor from nano to vim. I have run the following commands: sudo update-alternatives --config editor and update-alternatives --config editor Both now output: ...
8
votes
3answers
41k views

How do I configure exim4 to send mail through a password protected ssl smtp mail server?

I'd like my cronjobs to be able to send mail from my home computer. My servers configure exim4 like this: dc_eximconfig_configtype='internet' dc_other_hostnames='' dc_local_interfaces='127.0.0.1' ...
5
votes
3answers
6k views

unattended-upgrades not running, /etc/cron.daily/apt missing

I have automatic-upgrades installed and configured, but it never seems to run, because there are always security updates waiting to be installed when I check. https://help.ubuntu.com/community/...
9
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2answers
13k views

Where are cron logs stored on Ubuntu 14.04?

I am trying to troubleshoot why my cron task isn't working sometimes. Where does cron store log files by default? Is it /var/log/syslog ? I have looked at that file and it is empty. Do I need to ...
8
votes
2answers
29k views

How to stop email report from Cron <root@machine> (hourly)

I'm running an Ubuntu 12.04, I've configured "ssmtp" with my gmail account and now I'm getting every hour an email with a report, this is an example: From: root <my@gmail.com> Date: 2012/8/13 ...
4
votes
3answers
3k views

Cron not able to succesfully change background

I'm running 12.04 with a custom XML background (modification on Day of Ubuntu) that changes based on time of day. I've noticed that there's a significant delay between when the changes are scheduled ...
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votes
1answer
14k views

Cannot run cron job for a php script

I want to run a php script using cron job on localhost my script is situated at - /opt/lampp/htdocs/rrugd/myscript.php now as opt is under root, i tried adding the cron job for root as well as ...
17
votes
4answers
58k views

How can I tell if my hourly cron job has run?

I have created a file called ntpdate in /etc/cron.hourly #!/bin/sh /usr/sbin/ntpdate-debian date > /tmp/william_tmp date > /william_tmp date > ~/william_tmp echo test I also did Chmod 755 ...
13
votes
4answers
12k views

Why does apt-get fail when automated with cron?

I'm trying to use cron to automate my system updates. You can see my crontab, commands, and resulting errors below. When I run upgrades.sh as root, the script runs fine. When cron runs it, apt-get -y ...
9
votes
3answers
769 views

How to persist on a wifi connection after disconnection?

I've got a Ubuntu machine running a software that requires internet. However, sometimes the wifi fails (router reboot for example) and doesn't find the network again, until I manually service network-...
8
votes
1answer
4k views

Hourly GIT Push

Is it possible for me to automate a Git push every hour via a batch script. I would typically type in this: git add * git commit -m "latest update" git push https://username:password@github.com/...
6
votes
2answers
9k views

What is my crontab -e local file path? I want to set it via BASH script

In my Ubuntu, my username is "meuser". When i do crontab -e, i can setup my rules. But instead of doing it with crontab -e, how can i do it directly to a file? Which file i cant modify?
4
votes
1answer
618 views

Editing Gsettings unsuccesful when initiated from cron

I must have a blind spot, but I cannot find what it is. I made a small python script that removes VLC from the sound menu. It runs perfectly in any way I run it from the terminal or from a launcher ...
3
votes
4answers
5k views

execute script after desktop loaded?

I want to execute bash script on startup that opens several terminals in different workspaces. Script works just fine if I call it from terminal, but it doesn't work if executed from crontab using @...
1
vote
2answers
975 views

Cron job fails for any time other than default * * * * *

On Ubuntu 11.10 (Oneiric Ocelot), my cron job run fine if I use the default * * * * * But if I want it to run at 17 hrs or any other time, it never runs. My settings are: 00 17 * * * wget http://...
12
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3answers
4k views

what can be causing /etc/cron.daily/apt to hang?

Lately I've been getting a mail from the server every day, Subject Cron <root@host> test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily ) Body /etc/cron.daily/...
7
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3answers
13k views

Daily cron job not running

A quick overview: I have a script that will daily backup my source code repository from SVN into a tarball for that day. I have tested the script and it works very well as long as I run it as sudo, ...
6
votes
1answer
2k views

Schedule to record video stream in VLC

I work at a school and have setup a workstation to broadcast/stream the morning announcements for the teachers and kiddos. Teachers in the classroom access this stream via Windows Media Player or VLC....
5
votes
1answer
1k views

Is there a programmable way to tell if the screen is locked?

I have lots of stuff in my crontab, including some that talks to my screen. If I'm not there for it to be notifying, I don't really want it to run. Is there a way I can check to see if the computer ...
5
votes
7answers
4k views

How to run cron job when network is up?

I have some anacron jobs which run daily. The scripts update local bzr and git repositories. Naturally these scripts need working network connections. I'm on a laptop and often wired and wireless ...
5
votes
3answers
4k views

Function of /etc/cron.hourly

If I create a script and then place it in this folder (/etc/cron.hourly), will my system run this script hourly? Or does my script need to begin with a command as well?